This invention pertains to apparatus for counting articles carried on a conveyor, or the like, and in particular, relates to such apparatus wherein counting accuracy is achieved through discriminating on the basis of the leading-edge profiles of successive traveling articles.
While it will be obvious to those skilled in the art that the instant invention has utility in a relatively wide range of applications, a preferred embodiment thereof is described herein in conjunction with the counting of newspapers--an application with respect to which it has been found to have particular utility.
Modern newspapers are printed, cut, assembled and folded at very high speeds. Completed newspapers are typically fed to an offbearing conveyor, with successive newspapers over-lapping one another with their leading, folded edges spaced several inches apart. A typical offbearing conveyor speed is about 4.5-feet-per-second.
The offbearing conveyor usually feeds what is known as a counter/stacker, wherein the oncoming newspapers are stacked, counted mechanically as they are stacked, and delivered in bundles of possibly differing predetermined numbers of papers, according to final destination. Conventional mechanical counting, however, in such a situation is often inaccurate. This is wasteful, and over time can seriously affect profitability.
A general object of the present invention is to provide a unique electro-optical non-contacting solution to the problem of counting conveyor-transported articles, such as newspapers.
More particularly, an object of the invention is to provide such apparatus for counting articles which offers an extremely high degree of accuracy and reliability.
Featured in the proposed apparatus is a laser which projects a beam to create reflections from the articles which are to be counted (in the case to be described below, newspapers), which reflections are imaged onto a linear photodetector array. The array is scanned recurrently to detect the presence and location of such an image, with the knowledge, from the geometry of the apparatus, that the position of such an image is directly related to the distance from the laser to the point of impingement with the reflecting article. Circuitry associated with the array produces, from such images, related output signals which are fed to a data-processing circuit. The latter circuit examines the train of incoming array signals to confirm the occurrence of a passing article. Such confirmation is based on the pre-known manner in which the successive leading-edge profiles of articles cause successive output signals from the array to be of a certain recognizable character. In the case of counting newspapers, naturally, it is the leading edge folded profile of the papers which generates a pattern of output signals in what was just referred to as a "pre-known manner".
As will be more fully explained below, with a stream of newspapers of the same folded size, and assuming for a moment that successive papers are arranged on a conveyor with a uniform condition of overlap, the highest points of the leading edges of the papers will lie at a certain distance above the transport plane of the conveyor. From pre-existing acquired data respecting passing, counted newspapers, or from assumed data supplied at the beginning of a run, as will be described, a reference threshold is established, regarding which the successive leading edges of adjacent papers will be characterized by a surface expanse which extends upwardly relative to the conveyor plane, immediately followed, for each given paper, by another surface expanse which generally parallels the conveyor plane for a short distance.
Signals which are generated by the array, as a result of laser-beam reflections from newspapers, are analyzed by the data-processing circuit to determine whether the points at which image reflections occur on the array indicate such a profile. The exact way in which this is accomplished will be explained fully in the description below.
Yet another important feature of the invention is that, at regular intervals during its operation (i.e., after a given number of confirmed counts), the threshold just referred to is adjusted to reflect any change which has occurred in the average of heights of the leading edges of the papers on the conveyor. This average is also referred to herein as the "effective" thickness of the papers. During a run of a given size newspaper, the situation can easily develop where papers, as distributed to the offbearing conveyor, become occasionally more closely overlapped, or more spread out. Also, it is well known that different runs of newspapers often comprise papers of different sizes (i.e., thicknesses). Adjustment of the threshold assures predictable count accuracy.
These and other objects and advantages which are attained by the invention will become more fully apparent as the description which now follows is read in conjunction with the accompanying drawings.